New Low-Toxicity Cholinium-Based Ionic Liquids with Perfluoroalkanoate Anions for Aqueous Biphasic System Implementation

This work explores the widening of properties of cholinium-based ionic liquids (ILs) through their combination with perfluoroalkanoate anions so that higher number of aqueous biphasic systems (ABSs) containing nontoxic cholinium-based ILs is available. For that purpose, six cholinium perfluoroalkanoate ILs were synthesized and their cytotoxicity was evaluated using three different animal cell lines, envisaging biotechnology applications. Ternary phase equilibrium data for ABSs composed of the cholinium perfluoroalkanoate, with fluoroalkyl chains from C₂ up to C₇, using a strong salting out agent, K₃PO₄, were determined at 25 °C. The results show the relevant role of the size of fluorinated alkyl chain length in the anion since, contrary to other ABSs containing ILs with increasing alkyl chain length in the anion, the ABSs with cholinium perfluoroalkanoates present well-spaced solubility curves, allowing the conclusion that these ABSs can be tuned by a proper choice of the IL. The phase splitting mechanism was also disclosed through water activity measurements